Acoustical system employing tubular resonators

ABSTRACT

Improved dispersion of the sound from an orchestra toward an audience and reinforcement of the lower frequencies in said sound are achieved through the use of tubular resonators positioned around and above the orchestra. Resonating chambers are formed in the ends of the tubes by means of transverse partitions. Electrically-driven speakers may be positioned in said tubes.

United States Patent Jaffe et al. I

[4 1 June 27,1972

[54] ACOUSTICAL SYSTEM EMPLOYING TUBULAR RESONATORS [72] Inventors:Christopher Jafle, 167 E. Rocks Road,

Norwalk, Conn. 06851; FrankO. Gehry, 1524 Cloverfield Blvd., SantaMonica,

1,969,704 8/1934 DAlton ..18l/3IA 2,122,447 7/1938 Zand ..l8i/48XFOREIGN PATENTS OR APPLICATIONS 687,525 '4/1930 France .181/30 337,90011/1930 01681131116111 ..l8l/33 GD 647,840 12/1950 GreatBritain ..l8l/33GD Primary Examiner-Robert S. Ward, Jr. Attorney-Alex Friedman et al.

[5 7] ABSTRACT Improved dispersion of the sound from an orchestra towardan audience and reinforcement of the lower frequencies in said sound areachieved through the use of tubular resonators positioned around andabove the orchestra. Resonating chambers are formed in the ends of thetubes by means of transverse partitions. Electrically-driven speakersmay be positioned in said tubes.

15 Claims, 6 Drawing Figures PATENTEDJUHN 1972 3, 672,463

SHEET 2 BF 2 INVENTORS film, 3W"

ATTORNEYS ACOUSTICAL SYSTEM EMPLOYING TUBULAR RESONATORS BACKGROUND OFTHE INVENTION It is frequently the case that in an auditorium where anorchestra is to perform for an audience, the acoustics may be such thatcertain frequencies or ranges of frequencies may be reinforced or may bediminished to such an extent that the sound of the orchestra, as heard,is seriously impaired. This unbalance may be the result of designing theenclosure principally for speech. For the understanding of speech it isdesirable that low frequencies be reduced; this is effected by the useof dropped acoustic ceilings and perforated ply-wood panels. The sameeffect is noted in large halls.

Need for bass reinforcement may also arise where the orchestralperformance is to be recorded. Some widely-used types of microphoneshave low efficiencies at the lower frequencies so that again bassreinforcement is needed.

The need for improved dispersion of orchestral sound arises,particularly, where the wall at the rear of the stage is parabolic inshape. The output of instruments close to the focus of the parabola isprojected directly forward whereas the sound from instruments away fromthe focus is projected to one side or the other. As a result, there areso-called deadspots on the stage. Devices to eliminate such deadspotsand improve the dispersion of the sound produced are thereforenecessary.

Devices for the improvement of dispersion are also needed for open-airperformances. Without the means to assure dispersion in the properdirections, a major portion of the sound output is lost.

SUMMARY OF THE INVENTION The present invention relates to a device forimproving the dispersion of sound toward an audience from an orchestraon a stage, and for reinforcing low frequencies in the spectrum of saidsound during the initial portion of reverberation. Vertical tubes arelocated on the stage at the sides and rear of the orchestra andhorizontal tubes are supported above the stage in a direction transverseto the stage and the orchestra. Some of the vertical tubes have chambersformed at the upper open end of a tube by a transverse partition. Also,some of the horizontal tubes have chambers formed at each open end ofthe tube by transverse partitions. The lengths of the chambers in thedifferent tubes vary in approximately equal steps from about /4 of thewavelength of the highest frequency to be reinforced to about /4 of thewave-length of the lowest frequency to be reinforced.

The upper ends of some of the vertical tubes may be cut at an angle inorder to broaden the band of wave-lengths reinforced by the tubes. Thesame may be done with the ends of some of the horizontal tubes. Thetubes may be used to house loud-speakers.

Accordingly, it is an object of the present invention to provideimproved means to reinforce desired frequencies in the spectrum of soundproduced by an orchestra.

Another object of the present invention is to provide means to improvethe dispersion of sound produced by an orchestra in order to avoid lossof sound energy to regions not occupied by an audience.

A further object of the present invention is to provide means to producereinforcement of sound in the lower frequencies without the need forsupplying electrical energy.

Still another object of the invention is to achieve reinforcement ofdesired frequencies and improved dispersion of sound with a low costdevice.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction,combination of elements, and arrangement of parts which will beexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWING For a fuller understanding of theinvention, reference is hadto the following description taken inconnection with the accompanying drawing, in which:

FIG. 1 is an elevational view of a stage and reflecting shell showingthe disposition of vertical and horizontal tubes for reinforcing anddispersing sound in accordance with the invention;

FIG. 2 is a plan view in partial section of the shell and tubes of FIG.1;

FIG. 3 is a view taken along line 33 of FIG. 2;

FIG. 4 is a view taken alongline 4-4 of FIG. 2;

FIG. 5 is an elevational view in cross section of a vertical tubeshowing the mode of establishing the length of a reverberation chamber;and

FIG. 6 is an elevational view in cross section of a vertical tubewherein the open end of a reverberation chamber is cut at an angle.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the presentinvention, the dispersion of sound from an orchestra performing on astage to an audience is improved by suitable disposition of largevertical tubes at the back and sides of the orchestra and by horizontaltubes disposed above the same orchestra. Moreover, using suitably placedtransverse partitions within the vertical and horizontal tubes to formreverberation chambers, each having an open end, selected bands offrequencies in the spectrum of sound coming from the orchestra can bereinforced.

A stage having a reflecting shell and tubes disposed in accordance withthe present invention is shownin FIG. 1, where shell 11 surrounds thesides, top and rear of stage 12. Vertical tubes 13 rest on stage 12 andare placed at the sides of the space to be occupied by an orchestra.Shell 11 is typical of one form of existing concert environment.

Horizontal tubes are placed above the area to be occupied by theorchestra and at a height such that mobility of the orchestra members isnot hampered. As is evident from FIGS. 1 and 2, the horizontal tubes runtransverse to the stage 12, that is, from side to side.

The diameter of the tubes, whether horizontal or vertical, may vary fromabout 1.5 feet up to about 4.0 feet. For dispersion of sound, theoptimum diameter is about 2 feet, whereas for reinforcement of bassfrequencies in the sound spectrum, a diameter of about 3 feet isoptimum. However, dispersion and bass reinforcement are achieved overthe entire specified range.

The need for reinforcement of low frequency tones arises from a numberof factors, as described above. Where the auditorium is designedprimarily for speech, the introduction of tubes above and around theorchestra in accordance with the present invention tends to rectify theimbalance caused by the construction of the auditorium. Also, where theperformance of the orchestra is being recorded, the proper dispositionof tubes in accordance with the invention compensates for the non-linearcharacteristic of the microphones. It should be noted that thereinforcement of the low tones persists for only about 250 microseconds,the rate of decay of each tone being more rapid when bass reinforcementis used.

The need for improved dispersion is particularly great in the case ofoutdoor performance. Under such conditions, the

amount of reverberation is relatively low and sound intensity as heardby the audience is likewise low. Properly placed tubes help to confinethe sound leaving the orchestra to the region occupied by the audience.Improved dispersion is particularly needed where the shape of thereflecting shell is essentially parabolic. With such a shell, movementof a player's head over a distance of a few inches can result in a sharpincrease or decrease in the sound reaching the audience. The tubes ofthe present invention prevent such an effect.

Bass reinforcement results from placing a transverse partition in a tubeas shown in FIG. 5. Chamber 15 is formed in tube 16 by means ofpartition 17. Since the chamber 15 has an open end 18, the chamber willreinforce a tone having a wavelength four times as great as the lengthof the chamber 15. Where it is desired to reinforce a band offrequencies ranging from say 37 cps to about 67 cps, the chambers shouldrange in length from about 4 feet 5 inches to about 8 feet 9 inches,preferably in roughly equal steps. The frequency reinforced by a givenchamber can be broadened into a band by cutting the open end of achamber diagonally as shown at 19 in FIG. 6.

Where electronic amplification is desired, speakers may be installed intubes as shown at 21 in FIG. 1. The removal of a panel from each tube infront of the speaker is necessary prior to installation of a speaker. Inthe embodiment shown in FIG. 1, the speakers are installed in tubes 22in what are termed offside tubes. However, speakers may be installed ifdesired in any of the horizontal tubes or the other vertical tubes whichare essentially contiguous to the orchestra. Also, speakers should notbe installed in tubes having a transverse partition to form areverberation chamber because specific frequencies would then be toostrongly reinforced.

As indicated above, the exteriors of the tubes aid in the dispersion ofthe orchestral sound. For maximum efiiciency in this regard, tubesshould be separated by no more than about 1!; their diameter. Also, itis preferable that the tubes at either side of the orchestra] space bealigned as shown in FIG. 2, roughly defining two divergent planes. Theangle between the planes should be such as to include the entireaudience space, but should not greatly exceed this value. Additionalvertical tubes are placed at the rear of the orchestra with theparticular objective of preventing anything resembling specularreflection from the rear of enclosure 11. The vertical tubes 22 areexterior to planes 23 and 24 defined by the vertical tubes at the sidesof the orchestra. These tubes provide some reverberation using soundreflected from the audience space or from rear and side walls andceiling if present. in some applications, vertical tubes only may beused; in such applications, horizontal tubes may be omitted because oflack of overhead space or because the vertical tubes alone givesufficient reinforcement and control of dispersion for the requiredpurposes.

Horizontal tubes may be hung above the orchestral space in such relationas to define a plane passing somewhat above all individuals in theaudience space. In a preferred arrangement, however, the horizontaltubes are disposed in groups of three as shown in FIG. 3. In each groupof three, the middle tube makes contact with the tube in front and thetube to its rear. The rearward tubes in each group define a plane 31which passes over the heads of all members of the audience. Such tubesare 26, 27, 29 and 30 in FIG. 3. However, the frontward tube in eachgroup here exemplified by 25 and 28 is displaced upward by about halfthe diameter of the tubes. Surprisingly, this arrangement has been foundto give superior dispersion of orchestral sound toward the audience, andparticularly toward the upper part thereof.

Tubes which have been found to be satisfactory for the objectives of thepresent invention are manufactured by Sonoco Products of Hartsville, S.C., under the name of Sonotubes. The tubes are used as concrete forms,are cylindrical and can be had over a range of lengths. For conveniencein shipping, tubes can be used in relatively short lengths and coupledtogether where needed.

The foregoing invention is especially useful in existing environments tosubstantially improve acoustical qualities for musical performances. Theconcepts of the invention are equally adaptable for permanent andtemporary installation in new and existing structures.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained, andsince certain changes may be made in the above construction withoutdeparting from the spirit and scope of the invention, it is intendedthat all matter contained in in the above description or shown in theaccompanying drawing shall be interpreted as illustrative and not in alimiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

What is claimed is:

1. A system for improving the dispersion of sound toward an audience,said sound being produced by an orchestra on a stage, and forreinforcing low frequencies in the spectrum of said sound during theinitial portion of reverberation, comprising vertical tubes on saidstage at the sides and rear of said orchestra and horizontal tubessupported above said stage in a direction transverse to said stage andsaid orchestra, at least some of said vertical tubes having a chamberwith one open end formed at the upper end of said tube by a transversepartition, and at least some of said horizontal tubes having a chamberwith one open end formed at each end of said tube by transversepartitions, the lengths of said chambers in the different tubes varyingin approximately equal steps from about 5 1 of the wave-length of thehighest frequency to be reinforced to about A of the wave-length of thelowest frequency to be reinforced.

2. A system as defined in claim 1, wherein said tubes have a diameter of1.5 to 4.0 feet.

3. A system as defined in claim 1, wherein an open end of at least onechamber in a tube, forms an angle with the axis of said tubesufficiently different from to cause said chamber to reinforce a band offrequencies.

4. A system as defined in claim 1, wherein said chambers range in lengthfrom about 4 feet 5 inches to about 8 feet 9 inches.

5. A system as defined in claim 1, wherein at least oneelectrically-driven speaker is mounted in a tube, a panel having beencut from the cylindrical wall of said tube to permit transmission ofsound through the resultant opening.

6. A system as defined in claim 1, wherein said vertical tubes are about1 foot apart.

7. A system as defined in claim 1, wherein said horizontal tubes lieclose to a plane which is lower toward the rear of the stage and highertoward the front of the stage, the frontward extension of said planepassing above the highest portion of said audience.

8. A system as defined in claim 7, wherein said horizontal tubes arepositioned in groups of three, the most forward tube in each group lyingabove said plane by about one-half the diameter of said tubes, thecentral tube of each group lying close to the other tubes of said group,said forward tube being thus positioned for the purpose of increasingthe fraction of said sound dispersed toward upper portions of saidaudience.

9. A system as defined in claim 1, wherein said vertical tubes havelengths between 13 and 30 feet and said horizontal tubes have lengthsbetween 35 and 75 feet.

10. A system as defined in claim 1, wherein the diameter of said tubesis about 2 feet, this diameter being optimum for dispersion of sound.

11. A system as defined in claim 1, wherein the diameter of said tubesis about 3 feet, this diameter being optimum for bass reinforcement.

12. A system as defined in claim 1, wherein said vertical tubes ateither side of said orchestra define two planes, which when extended,include between them all individuals in said audience.

' 13. A system as defined in claim 1, wherein said vertical tubes at therear of said orchestra are disposed in a plane.-

14. A system as defined in claim 1, wherein the exterior surfaces ofsaid vertical tubes are spaced, one from the other, by a distance nomore than A: the diameter of the tubes.

15. A system for improving the dispersion of sound toward an audience,said sound being produced by an orchestra on a stage, and forreinforcing low frequencies in the spectrum of said sound during theinitial portion of reverberation, comprising vertical tubes on saidstage at the sides and rear of said orchestra, at least some of saidvertical tubes having a chamber with one open end formed at the upperend of said tube by a transverse partition, the lengths of said chambersin the different tubes varying in approximately equal steps from aboutV4 of the wave-length of the highest frequency to be reinforced to about/4 of the wave-length of the lowest 5 frequency to be reinforced.

1. A system for improving the dispersion of sound toward an audience,said sound being produced by an orchestra on a stage, and forreinforcing low frequencies in the spectrum of said sound during theinitial portion of reverberation, comprising vertical tubes on saidstage at the sides and rear of said orchestra and horizontal tubessupported above said stage in a direction transverse to said stage andsaid orchestra, at least some of said vertical tubes having a chamberwith one open end formed at the upper end of said tube by a transversepartition, and at least some of said horizontal tubes having a chamberwith one open end formed at each end of said tube by transversepartitions, the lengths of said chambers in the different tubes varyingin approximately equal steps from about 1/4 of the wave-length of thehighest frequency to be reinforced to about 1/4 of the wave-length ofthe lowest frequency to be reinforced.
 2. A system as defined in claim1, wherein said tubes have a diameter of 1.5 to 4.0 feet.
 3. A system asdefined in claim 1, wherein an open end of at least one chamber in atube, forms an angle with the axis of said tube sufficiently differentfrom 90* to cause said chamber to reinforce a band of frequencies.
 4. Asystem as defined in claim 1, wherein said chambers range in length fromabout 4 feet 5 inches to about 8 feet 9 inches.
 5. A system as definedin claim 1, wherein at least one electrically-driven speaker is mountedin a tube, a panel having been cut from the cylindrical wall of saidtube to permit transmission of sound through the resultant opening.
 6. Asystem as defined in claim 1, wherein said vertical tubes are about 1foot apart.
 7. A system as defined in claim 1, wherein said horizontaltubes lie close to a plane which is lower toward the rear of the stageand higher toward the front of the stage, the frontward extension ofsaid plane passing above the highest portion of said audience.
 8. Asystem as defined in claim 7, wherein said horizontal tubes arepositioned in groups of three, the most forward tube in each group lyingabove said plane by about one-half the diameter of said tubes, thecentral tube of each group lying close to the other tubes of said group,said forward tube being thus positioned for the purpose of increasingthe fraction of said sound dispersed toward upper portions of saidaudience.
 9. A system as defined in claim 1, wherein said vertical tubeshave lengths between 13 and 30 feet and said horizontal tubes havelengths between 35 and 75 feet.
 10. A system as defined in claim 1,wherein the diameter of said tubes is about 2 feet, this diameter beingoptimum for dispersion of sound.
 11. A system as defined in claim 1,wherein the diameter of said tubes is about 3 feet, this diameter beingoptimum for bass reinforcement.
 12. A system as defined in claim 1,wherein said vertical tubes at either side of said orchestra define twoplanes, which when extended, include between them all individuals insaid audience.
 13. A system as defined in claim 1, wherein said verticaltubes at the rear of said orchestra are disposed in a plane.
 14. Asystem as defined in claim 1, wherein the exterior surfaces of saidvertical tubes are spaced, one from the other, by a distance no morethan 1/3 the diameter of the tubes.
 15. A system for improving thedispersion of sound toward an audience, said sound being produced by anorchestra on a stage, and for reinforcing low frequencies in thespectrum of said sound during the initial portion of reverberation,comprising vertical tubes on said stage at the sides and rear of saidorchestra, at least some of said vertical tubes having a chamber withone open end formed at the upper end of said tube by a transversepartition, the lengths of said chambers in the different tubes varyingin approximately equal steps from about 1/4 of the wave-length of thehighest frequency to be reinforced to about 1/4 of the wave-length ofthe lowest frequency to be reinforced.